'87 C3.2L bucking when taking off question

[Tippy]

I just rebuilt my '87 C3.2L (has 3.4 Mahle/Max Moritz P&C's) recently and right at the 500 mile mark, I got this bucking/surging symptom. I rebuilt it due to a "money shift" BTW.

Background of engine:

1. 3.4 P&C's (7.5:1 CR)
2. T60-01 Turbonetics - 1-bar
3. Equal length T4 headers
4. Full bay IC
5. Twin -044 pumps
6. Protomotive RRFPR
7. EFI is 100% stock with blow-though AFR except chip burned by Protomotive and no oxygen sensor
8. All else is stock in the engine

Anyways, I bought the car the way it is and have touched nothing regarding ignition or FI before and after the rebuild.

So, the day I got the "bucking" while taking off from a light symptom, was after a 4th gear pull hitting 1.2 - 1.3bar (for a split second) when heading to work. This has happened before where I had overboost but I quickly let off so I wouldn't do any damage.

During lunch that day is when I tried to take off from work and this happened. It did it every time I took off but once going, say above 2000 or so or kind of heavy on the gas, it was good to go. Under boost, it is good too. No problems. I should add, it also backfired through the exhaust a few times but not a large backfire, more of a slight backfire FWIW.

This is what I have already checked:

1. Retightened intake which was loose but not the culprit after test drive
2. Cap and rotor fine
3. Spark plug wires all attached and also the coil wire
4. Microswitch for the right-off-idle, turn the fuel back on (not sure of name?), on the backside of TB is clicking but not confirmed if working with a test meter
5. Looked at all vacuum hoses and found nothing loose or cracked - still need further investigation though
6. The intake tract past the MAF to the throttle body looks sealed
7. Cylinder head temp sensor is fairly new

I need to test for vacuum leaks with some ether or propane. I've yet to do this but will get to tomorrow.

The only thing I can think that may be a possibility is the huge hose going to the brake booster. I intend on clamping closed seeing if it is it.

Next will be pulling plugs and seeing if anything is abnormal

Any other thoughts?

[DRACO A5OG]

Check your distributor, remove rotor and see if there is up/down play on the shaft. if so shims are gone.

[Tippy]

The shaft has nearly 0 play. I just replaced it during rebuild. Thx

[Tigerrat]

How about the wiring and connectors to the CHT and flywheel sensors? A CHT problem can cause the bucking and those connectors can deteriorate with heat and age. Ken

[Tippy]

Yeah, I read that too. I'll take a look again. Thx